Semiconductor memory devices include memory cells for the storage of electronic information. Non-volatile memory devices enjoy widespread use because their associated memory cells can retain information even when the source power supply is disabled or removed. This feature makes non-volatile memory devices especially attractive for use in portable electronics. With the continuous trend toward higher integration, high-density layout, low-power operation, and high operating speed are common considerations for such devices.
One type of non-volatile device, referred to as flash memory, has become popular because it is relatively inexpensive to produce, and because it operates at relatively low power demands; however, flash memory is known to generally suffer from low operating speed, relatively poor data retention reliability and relatively short life span. In addition, such devices are based on the operation of conventional transistors, and with the pressures of further integration, they increasingly suffer from the short-channel effect, lowering of breakdown voltage, and lowering of reliability of the gate junction with repeated program/erase cycles. In addition, as the size of the transistor decreases, there is an increased likelihood of intercell interference, which can have a further adverse effect on performance and reliability.